Parc nationalthumb|Parc national Los Cardones en Argentine. thumb|Hiver en Wattamolla au Parc national Royal en Australie. thumb|Parc national de la forêt de Bavière, en Allemagne. Un parc national est une portion de territoire dans laquelle la faune, la flore et le milieu naturel en général sont protégés des activités humaines. Son intérêt peut être aussi touristique, car les parcs nationaux attirent chaque année de nombreux visiteurs.
Stock and flowEconomics, business, accounting, and related fields often distinguish between quantities that are stocks and those that are flows. These differ in their units of measurement. A stock is measured at one specific time, and represents a quantity existing at that point in time (say, December 31, 2004), which may have accumulated in the past. A flow variable is measured over an interval of time. Therefore, a flow would be measured per unit of time (say a year). Flow is roughly analogous to rate or speed in this sense.
Asset classesIn finance, an asset class is a group of financial instruments that have similar financial characteristics and behave similarly in the marketplace. We can often break these instruments into those having to do with real assets and those having to do with financial assets. Often, assets within the same asset class are subject to the same laws and regulations; however, this is not always true. For instance, futures on an asset are often considered part of the same asset class as the underlying instrument but are subject to different regulations than the underlying instrument.
